Power supplies for electrical systems have been utilized for a century or so. As time progressed new uses of electrical systems placed a need for more sophisticated systems.
One particular utilization is the need for power transfer to the utilization device but yet with the requirement that there be power isolation.
The advancement of electronics and power devices such as SCRs, Triacs and the such, appeared to be an obvious solution to such a power transfer. Current limiting circuits also were developed. Unfortuneately, the solution was not met. The electronic devices in most instances could not limit or tolerate high power.
Finally, it became apparent that the electrical systems, with this type of current limiting requirement necessitated electrical power supplies--not electronic.
A very uneffective device is the auto alternator that will provide an increased power output with limited current. However this device, too, with it's sufferings, such as opposing magnetic fields, rubbing contacts and the such, made this device very inefficient.